Function

[NRAM_I75A5] Catalyzes the removal of terminal sialic acid residues from viral and cellular glycoconjugates. Cleaves off the terminal sialic acids on the glycosylated HA during virus budding to facilitate virus release. Additionally helps virus spread through the circulation by further removing sialic acids from the cell surface. These cleavages prevent self-aggregation and ensure the efficient spread of the progeny virus from cell to cell. Otherwise, infection would be limited to one round of replication. Described as a receptor-destroying enzyme because it cleaves a terminal sialic acid from the cellular receptors. May facilitate viral invasion of the upper airways by cleaving the sialic acid moities on the mucin of the airway epithelial cells. Likely to plays a role in the budding process through its association with lipid rafts during intracellular transport. May additionally display a raft-association independent effect on budding. Plays a role in the determination of host range restriction on replication and virulence. Sialidase activity in late endosome/lysosome traffic seems to enhance virus replication.

Evolutionary Conservation

Publication Abstract from PubMed

A phosphonate analog of N-acetyl neuraminic acid (PANA) has been designed as a potential neuraminidase (NA) inhibitor and synthesized as both the alpha (ePANA) and beta (aPANA) anomers. Inhibition of type A (N2) and type B NA activity by ePANA was approximately a 100-fold better than by sialic acid, but inhibition of type A (N9) NA was only ten-fold better than by sialic acid. The aPANA compound was not a strong inhibitor for any of the NA strains tested. The crystal structures at 2.4 A resolution of ePANA complexed to type A (N2) NA, type A (N9) NA and type B NA and aPANA complexed to type A (N2) NA showed that neither of the PANA compounds distorted the NA active site upon binding. No significant differences in the NA-ePANA complex structures were found to explain the anomalous inhibition of N9 neuraminidase by ePANA. We put forward the hypothesis that an increase in the ePANA inhibition compared to that caused by sialic acid is due to (1) a stronger electrostatic interaction between the inhibitor phosphonyl group and the active site arginine pocket and (2) a lower distortion energy requirement for binding of ePANA.